Problem: $ { \left[\begin{array}{rrr}{2} & {4} & {4} \\ {-1} & {2} & {-1}\end{array}\right]+\left[\begin{array}{rrr}{-1} & {1} & {-1} \\ {3} & {2} & {0}\end{array}\right] = {?} } $
To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{2}+{-1} & {4}+{1} & {4}+{-1} \\ {-1}+{3} & {2}+{2} & {-1}+{0}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{1} & {5} & {3} \\ {2} & {4} & {-1}\end{array}\right]}$